More shroud refactoring.

This introduces a hash on Shroud which ShroudRenderer
can observe, removing the need to explicitly twiddle
a dirty flag between objects.

Shroud disabling is now done via RenderPlayer, so
enabling the cheat or winning/losing will now give
vis equivalent to an observer.

OpenRA.Game/Player.cs

@@ -77,7 +77,7 @@ namespace OpenRA
 			}
 			PlayerActor = world.CreateActor("Player", new TypeDictionary { new OwnerInit(this) });
 			Shroud = PlayerActor.Trait<Shroud>();
-			Shroud.Owner = this;
+
 			// Enable the bot logic on the host
 			IsBot = botType != null;
 			if (IsBot && Game.IsHost)